My house is quite old so about 8 years ago we removed the picture rail in the family room leaving one wall (i had plasterboarded the others)stepped in from where the rail was up to the ceiling. We brought in a plasterer who remedied the step condition and continued with a light skim all over the wall so that there would be no obvious seam under the soon to be applied wallpaper. He did do a good job, however, now that we are re-decorating and have stripped the paper from that particular wall some of the light plaster skim has come off with the wallpaper leaving large patches of missing plaster. As i said earlier,i intend to re-wallpaper the room Is there any proprietary type repair material that a reasonably capable DIY person could apply without having to call in a plasterer again.